overheating help

[mva5142]

I recently became the owner of a 98 legacy outback with 80,000 miles on her. It has the 2.5l dohc. It overheated and after searching through the post on here I think it is the headgaskets. It overheated fast, cooled down to normal operating temp fast, and the lower radiator hose is much cooler than the upper. I have a couple questions so far.

1) why is there such a dramatic difference in the hose temperature?

2)There are no air bubbles or oil in the radiator or fill cap or water in the oil.

3)The car can idle all day and not overheat, why is this.

4)Can someone smarter than me explain why the headgasket leak causes these particular issues?

I have never worked on flat engine. I have done a couple head gasket jobs in the past on a rodeo and a mustang, is this engine especially complicated. Does the engine really have to get pulled to take the heads off?

Thanks all, looking forward to joining and participating in the community here.

Matt

[Zahmin89]

1) For some reason, Subaru tends to route coolant differently than other manufacturers. The top hose is usually the heated coolant coming from the engine and the bottom hose usually goes through the thermostat back to the engine, thus the lower hose should be cooler.

2) Just because there is a blown head gasket does not necessitate either of those things, it can show itself in many different ways, it just depends on the case. You may be low on coolant or even have an improper coolant/water ratio. Have you checked your radiator to see how much coolant there is in it? have you checked your recovery bottle? If it is dry chances are that your radiator is low.

3) That is often a symptom of low coolant. It's just like trying to heat your car in the winter, though. If you let it idle it takes 20 minutes to reach operating temp, but if you drive it, it comes up to temp a lot faster.

4)Basically, a head gasket goes between your cylinder head and your block. Your block has pathways in it for oil, coolant, fuel, air, etc. The gasket keeps these things sealed from each other. When there's a leak in a head gasket, it might cause coolant to flow into the cylinder, or oil into coolant, or coolant into exhaust, depending on how the crack forms. When coolant is not going where it is supposed to, your heads and your block can warp, making the problem even worse.

Before you consign it to being a blown head gasket, check the following:

Is there a lot of condensation in your exhaust?
Check your dipstick, is there a mayonnaise-y substance on it? or on your oil cap?
Is your air filter wet?
Is your coolant recovery bottle low? is your radiator low?

Also, flathead engines are easier to work on for head-related jobs simply because they're less complicated than other types.

[RahX]

Not necessarily. The DOHC is by no means easy. SOHC->DOHC->Turbo DOHC (only because the turbo is in the way and the nuts/bolts won't come off easy)->H6. Have you tried replacing the thermostat yet? It is a cheap and easy fix if it is the problem. Get Subaru coolant and the Subaru cooling system conditioner no matter what you do.

[Zahmin89]

OHC and OHV engines are not flathead engines. However when i read his post i was thinking about an 85 GL my friend had rather than the 98 outback in question. Being a 98 it would be SOHC or DOHC, I am not sure which without knowing his VIN.

[RahX]

Originally Posted by Zahmin89

OHC and OHV engines are not flathead engines.

Not 100% sure of what you're trying to say there?

[Zahmin89]

The heads on overhead cam (and overhead valve) engines are different from (and more complicated than) what is traditionally referred to as a "flathead", these days the only place to find a true flathead engine is in like a lawnmower or something.

[RahX]

OOOHHH I should have noticed that in his post earlier. I think he was referring to the boxer engine and mistakenly referred to it as a 'flathead'

[Zahmin89]

me too :P